Electron discharge device



NOV.8, 1938. B T I 2,136,105

ELECTRON DISCHARGE DEVICE Filed Sept. 3, 1956 TIME V POTf/VIML INVENTORQUNTHER JOBS! PUTENT/AL I Y i RNEY n K I] 341411 ANODE l L Patented Nov.8, 1938 aren't ELECTRON DISCHARGE DEVICE Giinther J obst,

Berlin, Germany, assignor to Telefunken Gesellschaft fiir DrahtlcseTelegraphic in. b. 11., Berlin, Germany,

tion of Germany a corpora- Application September 3, 1936, Serial No.99,231

In Germany 1 Claim.

My invention relates to electron discharge de' vices intended for theproduction of oscillations and more particularly to improvements indevices of the negative resistance type in which 5 with high anodepotentials less current is taken by the anode than with smaller anodepotentials.

The principal object of my invention is to provide an electron dischargedevice which can be used for amplification, rectification, mixing difl'ferent frequencies or for producing oscillations, and particularly toprovide an improved type of such device having a negative resistancecharacteristic.

The novel features which I believe to be char-- acteristic of myinvention are set forth with particularity in the appended claims, butthe in vention itself will best be understood by reference to thefollowing description taken in connection with the accompanying drawingin which Figure 1 is a diagrammatic representation of an electrondischarge device. embodying my invention, and a circuit therefor; Figure2 is a graphical representation of the operation of the device shown inFigure 1 under different conditions of anode voltage; Figure 3 shows acircuit arrangement embodying my invention; Figure 4 is a graphicalrepresentation of anode voltage con ditions during operation of thecircuit embodying my invention and shown in Figure 5; Figure 5 showsanother circuit arrangement embodying my invention; and Figure 6 is adiagrammatic representation of a modification of an electron dischargedevice embodying my invention.

By extending the field of application of the arrangement to very shortwaves where the transit time of the electrons is of importance withrespect to the length of the period of the action, the more generalformulation of above conditions applies namely that on the electronsthat are taken upby anode the work (t) ALVA ds f be 45 nifies theelementary quantum, Vac the anode direct potential,

o O as E8t -55 controlled, which fulfills the condition above ex-September 18, 1935 pressed, or on secondary electrons, ions or spacecharge effects, or in the Barkhausen-Kura case on a sorting out of theelects in the present case the variable penetrability of the anode withrespect to the electrons as a function of the anode potential orelectron speed is the means relied upon for fulfilling the abovecondition.

There is produced by the thus presupposed variable penetrabilityrelationship between potential in which there is first an increase ofthe internal resistance of the discharge plane with increasedpenetrability and with further inproperties of the anode a anode currentand anode crease of penetrability of the anode as a function of a risinganode potential, a reversal of the sign of this resistance or adecrease. The latter action takes place when the internal resistance isalready high due to additional means such as a screen grid between thecathode and anode or when working on the saturation point of the cathodefilament. In case the resistance of the cathode-anode discharge path isalready statically or dynamically negative due to some cause or other,for example controlling the grid in suitable phase, the means providedfor the penetrability variation as a function of anode potential can beconsidered as adding these properties and result for instance in areduction of the absolute value of the negative resistance or in animprovement of the efficiency.

It has been known since the experiments of Lenard that thin foils of ametal with small atomic weight for electrodes are the more permeable thehigher the electron speed. In this manner the prior art was successfulin having electrons with high potential leave the vessel throughmetallic foils that formed the closure of a vacuum vessel against air.The so-called Lenard windows nevertheless have still considerablethickness in order to be able to withstand the difference in airpressure between vacuum and atmosphere so that they have a properpermeability only for electrons of very high speed. If however, as canbe done with the means available at the present state of the art,optically transparent foils are used as anodes inside the tube,eliminating a mechanical stress in above sense, the penetration of theanode is achieved at relatively small anode potentials or electronspeeds. (See for instance German pattent 587,113, which likewiseproposes the use of such a thin metallic foil, however for the entirelydifferent purpose of releasing secondary elec trons by the penetratingprimary electrons.) During the passage through the anode the electronsare subjected to an average velocity loss which results in a heating ofthe anode, and with smaller anode potentials or lesser electron speedsthe passage of the electrons through the anode is prevented. The greaterthe anode potential or speed of the electrons the greater theprobability of the electrons passing through the anode and the smallertherefore the anode current. The electrons passing through the anode arecaught by an electrode disposed behind the anode: or the electrons maybe reflected in the case of very short waves. In the first case thiselectrode may be a solid sheet or dense net and is impressed with aslightly positive potential, in the case of short waves it may have anegative potential.

In accordance with my invention I reproduce the atomic field conditionsexisting in the interior of metal foil electrodes by means of anarrangement of coarser type. Just as within the atoms the electron pathsare more curved and finally are bound in the atomic bond, the smallerthe speed of the shot-through electron, in the same way the electronpaths are curved by means of the arrangement shown diagrammatically inFigure 1 in which the anode A consists of a pair of interposedelectrodes for instance one of bars ill and the other of plates or slatsII in alternating succession. Between these electrodes there is applieda constant potential difference and the higher potential is applied tothe larger electrode or to the electrode comprising the plates. Withhigher anode potentials and hence greater electron speeds in theneighborhood of the anode the electrons are deflected relatively only alittle by this potential difference and fly through the anode. For thecase where the anode potential or electron speed in the vicinity ofanode is small, the electrons are deflected much more strongly and sothat most of the electrons move toward the more positive part of theanode. An electrode S positioned between the cathode K and the anode Ais positively biased with respect to the cathode for accelerating theelectrons from the cathode to the anode.

In Figure 2a the path of the electrons from the cathode K through theanode A to the plate P is designated by the lines provided with thearrow heads. It will be observed that under these conditions of highplate voltage that the electrons pass through the anode without beingdeflected to any considerable extent. In the case shown in 2b with thelower anode voltage applied, the electrons are deflected from their pathand are caught and retained principally by the plate portions of theanode electrode.

In the circuit shown in Figure 3 an oscillating circuit comprising aninductance l2 and capacity I 3 is connected between the cathode K andthe anode A. The fixed potential difierence between the two electrodesforming the anode may be established by a resistance and condensercombination M or by a suitable source of voltage in the form of abattery.

A type of feedback arrangement for producing oscillations is shown inthe circuit in Figure 5. The plate electrode portion of the anode isconnected to an intermediate point on the inductance 15 which is bridgedby a capacity I6 to provide a tuned circuit. A battery I! is connectedbetween the tuned circuit and the rod electrode portion of the anode sothat the rod portion is at a lower potential. The voltage relationshipon the rod portion of the anode and the plate portion of the anode isshown in Figure 4, which represents the voltage relationship withrespect to time during operation of the tube. The lower fixed potentialE1 represented by the lower horizontal line is that applied to the rodelectrode portion of the anode, the AC potential existing on thisportion of the electrode being represented by the curve whose axis isthe fixed potential E1 applied to this electrode. The higher positivepotential E2 is applied to the plate electrode portion of the anode andthe superimposed AC potential is shown as the curve whose axis is thehorizontal line representing E2. While a battery i1 is shown in Figure5, it is of course possible to substitute a resistor and condensercombination such as shown in [4 of Figure 3.

While in the arrangements above the more or less large penetrability ofthe anode is the result of the field relations inside the anode proper.I may use an arrangement where the combination of elements produceselectron shadows and hence electron beams, for instance diaphragms usedin cooperation with geometrically adapted constructions of the anode tofurnish the desired effect. It is for instance a well known fact that inlarger tubes the grid struts shadows on the anode whereby it may bedirectly observed that the points of anode impinged upon glow, while theones not or less impinged upon appear dark. According to the potentialimpressed on the grid causing the shadow and on the anode, these lightand shadow points have different locations on the anode. By perforatingor cutting out those portions of the anode which are primarily impingedupon with higher potentials I can produce the desired result. Factors tobe considered for the geometric development of the tube depend uponwhether the electron distribution on the anode is produced by ashadowthrowing electrode of fixed potential or of alternating potentialcoupled with the anode potential. Particularly in the latter case theoptimum perforation or cutting out with respect to efiiciency may bemade only for definite operating conditions with respect to theamplitudes of anode and grid alternating potentials as well as thedirect potentials. The experimental basis for the placing of theseperforations is obtained for example with the aid of a model tube of thetype here in question which may be photographed for the momentary valuesof the potential combination. From these pictures are obtained thepoints to be perforated or cut out for a certain purpose of application.It may be pointed out that the perforations must not be-of such sizethat thereby considerable field variations, as compared to the field ofthe non-perforated or cut out anode, may occur at remoter distances fromthe cathode. The purpose in view would thus not be gained for theelectron path would be deflected too early in the direction of the solidparts of anode.

A further embodiment of my invention is shown in Figure 6. The electronspass through a diaphragm S having an aperture and to which is applied apositive potential with a certain velocity given by this potential andare deflected by the field of the anode disposed parallel to the path ofthe electrons passing through the diaphragm. If the anode potential islarge, the deflection is greater, and the electrons fly through theperforated part A in the vicinity of the slot and land on the pick-upsurface P located in the rear thereof. With smaller anode potentials thedeflection of the electrons by the transverse field is less and theelectrons land accordingly on the non-perforated parts of the anode A.

and wires form electron It may be added that the pick-up electrode lastreferred to may also be impressed with an alternating potential ofsu'table phase It is thus for instance possible to modify the circuitsin Figures 3, 5 and 6 in such a manner that the pick-up electrode isimpressed with a potential having a phase rotation of 180 with respectto the anode potential. But is must not in turn influence the control inthe vicinity and inside the anode. This and the passage of secondaryelectrons from the one to the other electrode may be prevented by a gridof suitable permeability and impressed with fixed potential andpositioned as a screen between P and A.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it

will be apparent that my invention is by no means limited to the exactforms illustrated or the use indicated, but that many variations may bemade in the particular structure used and the purpose for which it isemployed without departing from the scope of my invention as set forthin the appended claim.

What I claim as new is:

An electron discharge device having a cathode and an anode permeable toelectrons, said anode comprising a pair of interposed electrodes ofdifferent size elements electrically insulated from each other and asecond electrode adjacent the anode for receiving the electrons whichpass through said anode, and a grid disposed between the cathode and theanode.

GiiN'rHER JOBST.

